title: Effect of ascorbic acid and X-irradiation on HL-60 human leukemia cells: the kinetics of reactive oxygen species.
abstract: Ascorbic acid (AsA) treatment is expected to be a potential cancer therapy strategy with few side-effects that can be used alone or in combination with chemotherapy. However, the combination of AsA, a free radical scavenger, with radiation is not clearly understood; conflicting data are reported for cancer cell death. We conducted this study to determine the effect of AsA treatment combined with X-irradiation and the role of reactive oxygen species (ROS) in HL-60 human promyelocytic leukemia cells. Additive cytotoxic effects were observed when the cells were exposed to 2 Gy X-irradiation after 2.5 mM AsA treatment. When catalase was added to the culture with AsA alone, the cytotoxic effects of AsA disappeared. X-irradiation increased intercellular ROS levels and mitochondrial superoxide levels. By contrast, AsA alone and in combination with X-irradiation decreased ROS levels. However, in the presence of catalase neutralizing H2O2, AsA alone or in combination with X-irradiation only slightly decreased the intercellular ROS. Moreover, AsA decreased the mitochondrial membrane potential, which is commonly associated with apoptosis. These results suggest that the reduction of ROS did not result from ROS scavenging by AsA, and AsA induced apoptosis through a ROS-independent pathway. This study reports that a combination of AsA with radiation treatment is effective in cancer therapy when considering ROS in cancer cells.
authors.affiliation: Department of Radiological Life Sciences, Division of Medical Life Sciences, Hirosaki University Graduate School of Health Sciences, Hirosaki, Aomori 036-8564, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Terashima
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Hosokawa
authors.forename: Hironori
authors.initials: H
authors.lastname: Yoshino
authors.forename: Masaru
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Toshiya
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001205:Ascorbic Acid / Q000008:administration & dosage*; D016166:Free Radical Scavengers / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007700:Kinetics; D007938:Leukemia / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism; D014965:X-Rays
chemical_list: D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D001205:Ascorbic Acid